In studies of radial keratotomy, we have demonstrated that changes in corneal shape are regulated by the cellular events of corneal wound healing and wound contraction. These events include: (1) the transformation of adjacent keratocytes to a myofibroblast-like cell containing a putative contractile apparatus comprised of alpha-smooth muscle (alpha-SM) actin, non-muscle myosin and alpha-actinin (ie stress fibers); and (2), the progressive alignment of stress fibers parallel to the long axis of the wound. The major objective of this proposal is to clearly identify the cellular mechanism underlying changes in wound gape. We propose as an overall mechanisms that corneal myofibroblasts actively participate in wound contraction by exerting a contractile (pulling) forces, which are critically influenced by the mechanical state or STRESS distribution of the surrounding tissue. In order to test this hypothesis we have: (1) developed an in vivo model of corneal wound contraction using a rabbit full-thickness corneal injury in which both the direction and amount of stress is altered by the placement of intracorneal compression sutures; (2) established an in vitro rabbit keratocyte model of wound contraction which shares essential pathobiologic features to in vivo wounds using a collagen lattice culture system under non-stressed (free floating lattice) or stressed (attached lattice) conditions; and (3) established morphologic and biochemical techniques to assess the effects of STRESS on the development and organization of myofibroblasts. Our specific aims are: (1) To determine the effect of STRESS on myofibroblast organization by comparing morphologically the orientation of stress fibers under (a) normal STRESS and (b) altered STRESS (compression sutures); (2) To identify the contractile characteristics of myofibroblasts by determining their morphologic response to released STRESS (suture removal) and by correlating changes in wound gape to the changes in orientation of stress fiber bundles (a) under normal conditions, and (b) after cytochalasin D treatment; (3) To correlate the organizational changes in type I collagen with changes in stress fiber orientation during (a) contraction of normal, altered and released STRESS wounds following injection of DTAF-labeled soluble collagen, and (b) in vitro contraction of attached and free floating lattice cultures; and (4) To determine the effect of STRESS on myofibroblast transformation by: a) comparing and contrasting the expression of smooth muscle specific proteins (ie alpha-SM actin) in normal keratocytes, myofibroblasts and attached and free floating lattice cultures; and, b) determining the effects of muscle antagonists (papaverine) and agonists (serotonin) on wound and lattice contraction. These studies should provide important insights into fundamental questions concerning the mechanism of wound contraction and the role of the myofibroblast in corneal wound repair.